Since the dawn of cultivation, man has created a myriad of crop forms which have provided a wealth of genetic diversity in most crop species. Yet an ever increasing world population, and the introduction of improved cultivars into the centers of crop diversity have caused serious erosion of much of the worlds indigenous crop germplasm. The seriousness of this problem has received growing national and international attention, especially during the past 10 years. However, much remains to be done if the worlds crop germplasm still extant is to be salvaged, properly conserved, and adequately utilized.
Conservation of Crop GermplasmAn International Perspective CSSA Special Publication Number Proceedings of a symposium sponsored by Divisions C-1, C-4, and A-6 of the Crop Science Society of America in Washington, DC, 14-19 Aug 1983 Editorial Committee W L Brown, Chm T T Chang M M Goodman Q Jones Managing Editor David M Kral Associate Editor Sherri H Mickelson 1984 Published by the CROP SCIENCE SOCIETY OF AMERICA 677 South Segoe Road Madison, WI 53711 Cover Design: Julia M Whitty Copyright 1984 by the Crop Science Society of America ALL RIGHTS RESERVED UNDER THE U.S COPYRIGHT LAW OF 1978 (P.L 94-553) Any and all uses beyond the limitations of the "fair use" provision of the law require written permission from the publisher(s) and/or the author(s); not applicable to contributions prepared by officers or employees of the U.S Government as part of their official duties Crop Science Society of America 677 South Segoe Road, Madison, WI 53711 USA Library of Congress Catalog Card Number: 84-72462 Standard Book Number: 0-89118-518-6 Printed in the United States of America Table of Contents Preface Page v Plant Exploration: Planning, Organization and Implementation with Special Emphasis on Arachis C E Simpson The International Germplasm Program of the International Board for Plant Genetics Resources (IBPGR) J T Williams " 21 A National Plant Germplasm System Quentin Jones 27 The Role and Experience of an International Crop-Specific Genetic Resources Center T T Chang 35 International Germplasm Collection, Conservation and Exchange at ICRISAT Melak H Mengesha , " 47 Germplasm Preservation-Germplasm Resources Louis N Bass 55 Preface Since the dawn of cultivation, man has created a myriad of crop forms which have provided a wealth of genetic diversity in most crop species Yet an ever increasing world population, and the introduction of improved cultivars into the centers of crop diversity have caused serious erosion of much of the world's indigenous crop germplasm The seriousness of this problem has received growing national and international attention, especially during the past 10 years However, much remains to be done if the world's crop germplasm still extant is to be salvaged, properly conserved, and adequately utilized A symposium dealing with certain aspects of this subject was held at the 1983 Annual Meetings of the American Society of Agronomy Jointly sponsored by Div A-6, C-1, C-4, and the Committee on Preservation of Plant Germplasm of the Crop Science Society of America, the symposium consisted of six invited papers each of which is included in this publication The subject matter ranged from a detailed description of the essential elements of successful plant exploration to the broadly defined goals, objectives, and operations of national (USA) and international (IBPGR) plant germplasm programs Also described are the gene resource programs of two of the International Agricultural Research Centers, IRRI and ICRISAT Germplasm conservation as practiced at the National Seed Storage Laboratory of the U.S Department of Agriculture completes the series The information contained herein, gleaned from many years experience under a wide variety of geographic and political conditions, should be of interest to individuals and institutions engaged in any aspect of plant genetic resources Certain of the papers should be of special interest to those institutions contemplating the development of new plant genetic resource centers Editorial Committee W L Brown, Chairman T T Chang M M Goodman Q Jones W F Keirn, CSSAPresident v Chapter Plant Exploration: Planning, Organization, and Implementation with Special Emphasis on Arachisl C E SIMPSON2 When one considers the writings of the great plant explorers-O F Cook, David Fairchild, N I Vavilov, Walter T Swingle, Frank N Meyer, and others-in addition to the many well-known botanists who were their antecedents and contemporaries, it seems odd for an inconspicuous plant breeder, limited to one genus, to prepare a "how-to-do it" chapter on plant exploration But times change as the people who pursue the field work of germplasm collection It is largely to the plant breeders, who must utilize the collections, that have fallen the duties of plant exploration, and it is to them and their administrative superiors that the remarks in this chapter will be addressed The subject matter implied by the title of this chapter and its illustration by the author's experience with Arachis L will be applicable largely to the geographic areas and countries in South America where the work was conducted It would be wishful to think that the problems presented to plant explorers in the Near East, Central China, Africa, or India, for example, would be resolved by the discussions presented in this chapter Nevertheless, there is common ground to all plant exploration, introduction, and germplasm conservation Contribution from the Texas Agric Exp Stn., Texas A&M Univ., College Station, TX TA no 18947 Associate professor, Texas Agric Exp Stn., Texas A&M Univ., Stephenville, TX 7640l Copyright © 1984 Crop Science Society of America, 677 South Segoe Road, Madison, WI 53711 Conservation oj Crop Germplasm-An International Perspective SIMPSON It is the purpose of this chapter to bring forward some of the strengths of our program and to turn our weaknesses to the critical light of this forum and subsequently to the readers of its proceedings The collection and preservation of germ plasm of cultivated crops and their wild relatives is recognized as an important aspect of plant breeding for improvement of commercial cultivars Collection of crop species probably had its beginnings well before recorded history as hunters first became gatherers, and later cultivators as civilization advanced Some of the earliest recorded expeditions for plant collections occurred around 1500 B.C Even though numerous expeditions occurred in the early history of the New World, extensive collections were made after passage of the Morrill Act in 1862 (2), which resulted in a subsequent increase in agricultural research through the land-grant universities which the act established Another significant factor at this time (1862) was the organization of the Department of Agriculture as a separate unit; and later (1898), the creation of the "Section of Foreign Seed and Plant Introduction" (5) Names which are synonymous to this era are Fairchild, N E Hansen, and Mark Carleton It is important to point out that in many cases, the interest and drive of an individual scientist has contributed more to the crop collections than institutional and/or governmental programs As one would expect, and as it should have been, the major crops received attention first Many lines of wheat (Triticum aestivum L em TheIl.), maize (Zea mays L.), cotton (Gossypium L spp.), sorghum [Sorghum bicolor (L.) Moench], rice (Oryza sativa L.), potato (Solanum tuberosum L.), and other crops were collected during the first 60 years of the 20th century Collections have come from three sources-primary centers of origin (Vavilov, cited from 5) or primary centers of diversity (8, 14); secondary centers of diversity; and/or sub-secondary centers The genus Arachis originated on the Southern Brazilian shield, probably well before a mid-Tertiary geologic uplift of the shield (11) Following a series of uplifts, the genus Arachis was dissected (along with the shield and lower peneplane) by downward moving soil and water The evolution of the sections and species has occurred in the various major river valleys and their tributaries on the South American continent (11, 20) Running water has obviously played a major role in the distribution of the geocarpic Arachis species (11, 28) Gregoryet al (10) divided the genus into seven taxonomic sections and indicated the known areas (in 1973) of distribution of the sections The known sectional distributions conformed geographically to certain river valleys or river valley systems The South American region consists of the primary center of origin and diversity of Arachis Krapovickas (21) described five secondary centers for cultivated peanut and Gregory et al (10) added a sixth on the South American continent Hundreds of introductions of peanut (A hypogaea L.) have come to the USA over the years in exchange programs (3), but it was not until 1959 (10) that intensive effort was made to collect wild species of Arachis The efforts of Gregory, Krapovickas, and Pietrarelli, 1959 to 1967 (10), greatly increased the available wild and cultivated Arachis germplasm Ham- PLANT EXPLORATION mons and Langford (3, 10) added significant materials to the collection in 1968 With concern over the genetic vulnerability of many crop plants (3, 8, 13, 15) a renewed international effort has been made to collect and preserve germplasm of all types (Note: The 1975 Agronomy Abstracts (23) had 26 papers dealing with germplasm resources and genetic vulnerability of crop plants.) The Consultative Group on International Agricultural Research (CGIAR) and the Food and Agriculture Organization (FAa) of the United Nations (UN), through the International Board for Plant Genetic Resources (IBPGR), have become instrumental in many of these collection activities (See other portions of this publication for IBPGR activities.) This chapter presents some guidelines for plant exploration planning and implementation using the collection of Arachis from December 1976 through May 1983 as a medium of illustration of the organization and execution of germ plasm acquisition and conservation The project was sponsored by IBPGR and supported in part by the agencies listed in Appendix I PLANNING General Planning for plant exploration expeditions must begin months or even years in advance of the actual trip(s) The first step in planning is the establishment of a consensus in the minds of scientific associates concerning the wisdom of acquiring the needed collections Examples of this type of approach can be sited for several crops, including rice (6, 18), sorghum (25), and peanut (24) These documents resulted from international gatherings of scientists More recently, several collection plans have been outlined by IBPGR (26, 27) Scientists interested in collection should become cognizant of the earlier activities of the national and international centers and IBPGR The second planning step is to provide the heads of the national and international agencies concerned, with the consensus, and to elicit from them the administrative support of a suggested proposal to request funds for acquiring germplasm materials In the peanut program these agencies included IBPGR, International Crops Research Institute for the SemiArid Tropics (ICRISAT), U.S Department of Agriculture (USDA), and the agencies of the several proposed cooperators (see Appendix I) Following the peanut germplasm workshop in Florida in 1975 (24), Gregory and Krapovickas corresponded with heads of several of these agencies in attempts to solicit interest and funds for Arachis exploration After administrative support from the several agencies is reasonably solid, step three should be initiated, i.e., the presentation to the appropriate agency of a closely reasoned proposal for the work, designating collaborating local scientists in the proposed area of collection, team members in the various countries, and a scheme for depositing collected materials in the home country, international research centers, and in the center of the researcher making the proposal In preparing the proposal, germplasm resources already collected and available need to be determined, as well as where additional re- SIMPSON sources may be located Primary and secondary centers of origin and/or diversity need to be identified For most major crops these areas have been well documented, (8) but for certain minor crops this may not be true A proposal for germ plasm collection of peanut was submitted to the IBPGR in January 1976 by Gregory and Krapovickas (12, 19) Subsequently, three additional proposals and revisions were submitted Figure shows the areas of proposed coverage by the various expeditions The first proposal was funded by IBPGR and the work began in November 1976 Any potential plant explorer is encouraged to read the IBP Handbook No 11, Genetic Resources in Plants (8), and collection manuals prepared by Chang et al (7) and Hawkes (16, 17) These publications have a wealth of pertinent information and will be of great benefit to a plant collector Location Detailed planning of an expedition begins with selection of an area to be collected Many factors can determine collection sites It may be advantageous to return to an area which has previously yielded (~ ,W 70 I 60 I so I 40 Fig Areas proposed to IBPGR for exploration for Arachis, 1976 to 1983 PLANT EXPLORATION genes for specific disease resistance Perhaps a collection has proven particularly compatible as a parent, but lacks a specific character such as disease resistance; therefore, the area needs to be recollected Further, specific collections may no longer be available in live germplasm banks Various herbaria of the world contain specimens of wild species and may prove excellent sources of information for collection sites Depending upon the crop being collected, it could prove useful to utilize Vavilov's centers of origin; however, for most species, more recent information is available (6, 8, 14) In the case of peanut, much of the older germplasm collections did not survive the introduction process; therefore, we were returning to acquire living materials We also had potential collection sites based on the other sources mentioned above Team Concept Team collection has definite advantages The work load can be distributed according to each person's interests and capabilities The amount of documentation of collections will vary with the capabilities of the team members Thus, it is a good idea to comprise a team with varied backgrounds, but all with an interest in germplasm collection and preservation In planning for an expedition, care must be taken not to make a collection team too large Funding may limit team size; however, the collection site can also place restrictions on the number of participants If collections are to be made in a developing country, team size should probably not exceed four members, and ideally, only three For example, if the only means of reaching a specific site is by single engine aircraft; a pilot, three team members, and a limited amount of collection gear will weigh 850 kg-the maximum load for common, small, fixed-wing aircraft In addition, arrival of three extra mouths to feed in a remote village and the need for three more spaces to sleep is usually all that can be accommodated Four or more people tend to "overload the system." When roads and vehicles are available, four team members will be in order A point of peak efficiency is reached at four; five or more give diminishing returns because time consumed in packing a vehicle or getting a meal prepared and eaten reaches a break-even point Also, most vehicles will have adequate space for four plus their luggage, collection gear, and collections More people will require a larger vehicle, which will likely not be available in most places It is extremely important in selecting a team to include a member from the country or state being collected Also, it is advisable to try to locate local people to participate on a day to day basis This may mean involving a local botanist or agronomist with only a passing interest in the goals of the expedition, but more often than not, these people contribute significantly to the success of a mission In some countries with more advanced systems of agricultural research and/or germplasm preservation, local participation will be mandated by law The Arachis collection team, 1976 to 1983, initially included the three base members from the 1959, 1961, and 1967 expeditions: W C Gregory, A Krapovickas, and J Pietrarelli From this nucleus the team(s) expanded to include C E Simpson, D J Banks, A Schinini, H Zurita 0., and J F M Valls (see Appendix I for professional affiliation of team INTERNATIONAL GERMPLASM AT ICRISAT 53 characters are identified whenever a diverse group of germplasm is evaluated and screened At times, even those lines that show susceptibility to a disease or pest offer a rare source of breeding material for other agronomically desirable traits For example, sorghum accessions IS-1082, 2122, 2145, 4663, 4664, 5470, 5484, 5566, 18551, and others have been identified as promising lines for shootfly resistance However, they are susceptible to grain molds Other sorghum germplasm lines such as IS620,621,5959, 7237, 8219, 9308, 9482, and 11234 are promising lines for grain mold resistance; yet they are susceptible to shootfly and stem borer (Hydraecia sp.) Likewise in pigeon pea, ICP-7035 has multiple resistance to wilt and sterility mosaic, but it is susceptible to blight ICP-7065 is resistant to blight, but highly susceptible to both wilt and sterility mosaic There are many more examples like these which could have been rejected for one reason, while useful sources for their other traits In conclusion, plant quarantine is a very useful and necessary activity A safe and rapid transfer of germplasm is vital for a sound crop improvement program A great many exotic crops are flourishing in many areas of the world as a result of international transfer and exchange of germplasm It is also true that new diseases and pests may be introduced with the germplasm into new areas Nevertheless, import of small, experimental quantities of seeds with appropriate safeguards based on sound biological principles can often be an answer to improving the genetic base of crops Much larger quantities of commercial seed often repeatedly enter a country with even greater quarantine risk but often with minimal or cursory inspection Yet, germplasm is the basic raw material for future development of commercial seed and to impose undue restrictions on its movement appears to be an unnecessary and misguided practice Considering the worldwide crop improvement program and in view of the plant breeder's remarkable success in developing high yielding cultivars, it is obvious that there are significant advantages associated with international germplasm exchange With careful handling, imaginative methods and more specific research on seed pathogen pest relationships, man should be able to save his valuable seeds ACKNOWLEDGMENTS I wish to thank all my colleagues in the Genetic Resources Unit, and Dr K L Mehra, director of National Bureau of Plant Genetic Resources, ICAR, New Delhi, India, for their assistance in reviewing and improving this paper I also wish to express my appreciation to the CPPTI and ICRISAT Quarantine Unit for their assistance and cooperation REFERENCES Central Plant Protection Training Institute 1981-1982 Annual report Rajendranagar, Hyderabad-500 030, A.P., India Chiarappa, L., and J F Karpati 1981 Safe and rapid transfer of plant genetic resources: A proposal for a global system FAO/UNEP/IBPGR Technical conference on Crop Genetic Resources AGP: 1981/M/6, FAO, Rome 54 MENGESHA Cocking, M R et al 1981 Aspects of plant genetic manipulation Nature 293(5830): 265 270 Gonzalez, H R 1977 Entomological p 25 28 In W B Hewitt and L Chiarappa (ed.) Plant quarantine in international transfer of genetic resources CRC Press, Boca Raton, FL Harlan, J R 1975 Crops and man American SOCiety of Agronomy, and Crop Science Society of America, Madison, WI Hawkes, J G 1981 Germplasm collection, preservation and use p 57-83 In K J Frey (ed.) Plant breeding II Iowa State University Press, Ames Hewitt, W B 1977 Pathological p 3-16 In W B Hewitt and L Chiarappa (ed.) Plant quarantine in international transfer of genetic resources CRC Press, Boca Raton, IL ICRISAT 1980 Annual report Genetic Resources Unit, ICRISAT, Patancheru, A.P., India p 253-259 1981 Annual report Genetic Resources Unit, ICRISAT, Patancheru, A.P India p 16-18 10 International Board for Plant Genetic Resources 1979 Seed technology for gene banks AGP: IBPGRI79/31 IBPGR Secretariat, Rome 11 Jain, H K 1982 Plant breeders' rights and genetic resources Indian J Genet 42:121128 12 Justice, O L., and L N Bass 1978 Principles and practices of seed storage USDAAgriculture Handb no 506 U.S Government Printing Office, Washington, DC 13 Khan, R P 1977 Plant quarantine: Principles, methodology, and suggested approaches p 289-308 In W B Kewitt and L Chiarappa (ed.) Plant health and quarantine in international transfer of genetic resources CRS Press, Boca Raton, FL 14 Leppik, E E 1969 List of foreign pests, pathogens, and weeds detected on introduced plants Plant Introduction Paper no 15, Beltsville, MD 15 Maude, R B 1973 Seed-borne diseases and their control p 325 335 In W Heydecker (ed.) Seed ecology Butterworths, Massachusetts 16 Mehra, K L., and R K Arora 1982 Plant genetic resources of India-their diversity and conservation Indian Council of Agricultural Research, National Bureau of Plant Genetic Resources, New Delhi 17 Mengesha, M H., and K E Prasada Rao 1981 Current situation and future of sorghum germplasm p 323-333 In Sorghum in the eighties; Proc of the Int Symposium on Sorghum 2-7 November ICRISAT, Patancheru, A.P., India 18 1982 World sorghum germplasm collection and conservation A paper approved for publication as C.P No 141, ICRISAT, Patancheru, A.P., India 19 Naidu, P H., and K K Nirula 1979 Quarantine important diseases of sorghum, pearl millet, chickpea, pigeonpea and groundnut Indian J Plant Protection VII (2) :175 188 20 Roberts, E H 1974 Viability of seeds Chapman and Hall Ltd., London 21 Saxena, N P., and A R Sheldrake 1979 Physiology of growth, development, and yield of chickpeas in India p 106-120 In Proc of the Int workshop on Chickpea Improvement 28 February-2 March ICRISAT, Patancheru, A.P., India Chapter Germplasm Preservation! LOUIS N BASS2 GERMPLASM RESOURCES Crop germplasm resources may be defined as the total array of living species, subspecies, and their genetic variants, which are, or may be, important to humanity's present and future welfare There are many aspects of designing, constructing, and developing a gene bank, such as design criteria, location, reliability of the power supply, etc., which could be discussed but are outside the scope of this presentation This discussion will be limited to preservation of germplasm resources, whether in a natural state or under controlled conditions Perpetuation of species in their natural habitat is, of course, highly desirable but not always either practical or possible Preservation of the total array of crop germplasm is a broad and difficult task Although most discussions on germplasm preservation have been centered around crops such as corn (Zea mays L.), wheat (Triticum spp L.), rice (Oryza sativa L.), sorghum [Sorghum hicolor (L.) Moench], cotton (Gossypium spp L.), and other major industrial crops, numerous other species are also important to preserve PRESERVATION METHODS In its broadest sense, preservation includes controlled environment storage of seeds and other plant propagules and maintenance of living plants, either under controlled conditions or as natural stands Because Contribution of the National Seed Storage Lab., Fort Collins, CO 80523 Research plant physiologist, USDA-ARS, National Seed Storage Laboratory, Fort Collins, CO 80523 Copyright © 1984 Crop Science Society of America, 677 South Segoe Road, Madison, WI 53711 Conservation oj Crop Germplasm-An International Perspective 55 BASS 56 the USA has no native germ plasm of the major crops, except sunflower (Helianthus annuus L.), and has to depend upon other countries for native or wild germplasm; it is not directly involved in a major way in the development or setting aside of natural areas for perpetuation of crop species and their wild relatives in their native environment The USA is, however, involved formally in preserving some introduced crop germplasm as living plants in clonal repositories and informally in arboreta, nurseries, and botanic gardens Some native germplasm is maintained in forest preserves, wild areas, prairie preserves, etc However, most germplasm in the USA, especially that of the major crops, is preserved as viable seeds stored under controlled environmental conditions Several publications discuss broad aspects of gene resources, genetic vulnerability, and germplasm conservation (James, 1967; Frankel and Bennett, 1970; National Academy of Sciences, 1972, 1978; Frankel and Hawkes, 1975; International Board of Plant Genetics Resources, 1975; Matsuo, 1975; Hawkes et aI., 1976; Frankel and Soule, 1981) The present value of germplasm preservation facilities may not be immediately apparent, but as time goes on they will become increasingly important Modern improved varieties are gradually encroaching on centers of crop origins so that pockets where disease and/or insect resistance are found are becoming more and more confined If materials from these pockets are not collected and preserved, they will be lost forever to plant breeders By placing such germplasm in appropriate preservation facilities, they will be available to plant breeders indefinitely One preserved valuable plant germplasm accession may later save an agricultural industry; thus, the benefits realized from one germplasm accession could conceivably pay for the construction of good preservation facilities and the cost of maintaining them for many years The international interest in the genetic diversity of plants of actual and potential use by humans principally for food, fiber, forage, and oil relates to the identification of geographic centers of genetic diversity on which much plant exploration has been based The present world situation makes it necessary for plant breeders and other scientists to intensify their efforts toward solution of the eventual population/food confrontation This will, no doubt, require new genetic inputs to solve the problems associated with expanded production under less than ideal environmental conditions SOURCES OF GENETIC DIVERSITY Gaps still exist in the available base of genetic diversity Sources having the greatest potential for genetic diversity include wild populations of crop species, wild relatives of cultivated species, and primitive varieties that often contain genes for disease and insect resistance As mentioned earlier, these resources are being rapidly depleted, displaced, or abandoned Therefore, there is a great urgency to identify the gaps in our genetic diversity and make the necessary collections to fill them Other sources of genetic diversity include obsolete cultivars, current cultivars, breeding lines, breeding stocks, and elite germ plasm which also need to be systematically collected and preserved The very nature of collecting and preserving crop genetic resources requires international cooperation (National Academy of Sciences, 1972) GERMPLASM PRESERVATION 57 TYPES OF GERMPLASM COLLECTIONS The International Board for Plant Genetics Resources (IBPGR) classifies assemblages of genetic resources as base, active, and duplicate collections (IBPGR, 1976; Cromarty et al., 1982) Base collections are intended for long-term preservation and may be comprised of: (a) substantial collections of a wide range of species; (b) substantial collections of a limited range of species; (c) significant and original special purpose collections; and (d) replicates of any or all of these Active or working colused for multiplication, evaluation, documentation, distribution, and use by plant breeders Duplicate collections are duplicates of base collections that are housed in a geographically different location for security purposes To further that cooperation, IBPGR has played a central role in the organization of a worldwide network of genetic resources centers Certain important conservation centers have been asked to accept responsibility for storage of major base collections, either on a world or regional basis Other centers have been asked to provide storage for duplicate collections of germplasm of the major crops and their wild relatives INTERNATIONAL NETWORK OF GERMPLASM PRESERVATION CENTERS International Research Centers International centers which have agreed to serve as world or regional depositories for base collections for the crops they are working with include: Centro Internacional de Agricultura Tropical (CIAT), Columbia, bean (Phaseolus spp L.); Centro Internacional de la Papa (CIP), Peru, potato (Solanum tuberosum L.); International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), India, millet [Panicum miliaceum L., Pennisetum americanum (L.) Leeke, and Eleusine coracana (L.) Gaertn.], pigeon pea [Gajanus cajan (L.) Huth], chickpea (Gicer arietinum L.), and peanut (Arachis hypogaea L.); International Institute of Tropical Agriculture (lIT A), Nigeria, African rice (Oryza glaberrima Steud.) and cowpea [Vigna unguiculata (L.) Walp.]; and International Rice Research Institute (IRRI), Philippines, rice (Oryza sativa L.) The International Center for Agricultural Research in Dry Areas (ICARDA), Syria, has agreed to serve in a world capacity for its priority crops when adequate storage facilities have been established (IBPGR, 1982) National/Regional Centers By the end of 1982, national/regional centers in Argentina, Belgium, Canada, Costa Rica, Ethiopia, German Democratic Republic, German Federal Republic, Greece, India, Italy, Japan, Netherlands, Nigeria, Philippines, Poland, Portugal, Spain, Sweden, Thailand, United Kingdom, USA, and USSR were participating in the IBPGR network of base centers for crop germplasm (IBPGR, 1982) 58 BASS Other Centers Germplasm is also preserved at various research institutes, universities, botanic gardens, arboreta, nurseries, and even in private collections However, germplasm in private collections is frequently difficult to locate Worldwide, more than 36 countries are active in the preservation of genetic diversity through maintenance of germplasm collections of one or more crops As of 1979, more than 75 centers had or were constructing seed storage facilities No estimate was available for the number of centers preserving vegetatively propagated germplasm (Ng and Williams, 1979) No estimate is available for the number of germplasm preservation centers planned or completed since 1979 UNITED STATES NATIONAL PLANT GERMPLASM SYSTEM Plants from which the USA derives most of its food and fiber were introduced from other countries because only a few crop plants are native With very little native crop germplasm and a shallow base of primitive cultivars, modern agriculture in the USA depends upon a coordinated system to introduce, evaluate, distribute, and preserve the germ plasm obtained from throughout the world Furthermore, the complexity of modern plant research demands an efficiently organized effort to assure that plant breeders get the germplasm they need No one local institution can be expected to provide the germplasm required by the array of breeders working with even a single crop In the USA, the National Plant Germplasm System (NPGS) is a coordinated network of Federal, State, and private sector institutions, agencies, and research units which work cooperatively to introduce, maintain, evaluate, catalog, and distribute all types of plant germplasm Primary financial and administrative support for the components of the system comes from the Agricultural Research Service (ARS) of the U.S Department of Agriculture (USDA) and from the State Agricultural Experiment Stations (SAES) Commercial plant breeders, seed trade interests, and private citizens also contribute to and support the system The mission of these cooperative units is to provide plant scientists, now and in the future, with the germ plasm needed to carry out their research The research programs thus supported are widely varied They include breeding new cultivars for increased yield and quality, for ease of harvesting, better processing and longer storage; for resistance to diseases, insects, mechanical damage, temperature extremes, unfavorable soil moisture, salinity, smog, and other environmental stresses; for erosion control, beautification, noise abatement, and resistance to fire; and as sources of medicinal and industrial chemicals The quality of operation of the system, under its funding constraints, is evidenced by the reasonably good status of our crop genetic resources The NPGS (Anonymous, 1981) seeks to contribute to the stability of the agriculture of the USA and of the world, to enhance its development, and to provide it with new vistas by fulfilling the expressed and continu- GERMPLASM PRESERVATION 59 ing needs of research workers for plant germ plasm drawn from worldwide resources The primary components of the NPGS are the Regional Plant Introduction Stations, special curators, clonal repositories, and the USDA-ARS-National Seed Storage Laboratory (NSSL) Regional Plant Introduction Stations The Regional Plant Introduction Stations are charged with the responsibility for introduction, multiplication, distribution, preservation, and evaluation of seed propagated plants for industrial and agricultural utilization The Coordinators of the Regional Plant Introduction Stations are the curators of the working collections which plant scientists draw upon for their day-to-day germplasm needs of most crop species There are special problems associated with the wide range of plant materials the Regional Plant Introduction Stations must maintain Each species has its own requirements for optimum growth and seed production Some species require special pollination, while others are self-pollinated Seed must be carefully dried to a safe level for storage at a temperature of around 5°C and 35 to 40% relative humidity (RH) Because of the need for frequent access to the seed samples, they cannot be stored in hermetically sealed containers Special Curators Within the NPGS special curators are used for certain large collections such as cotton (Gossypium spp L.), flax (Linum usitatissimum L.), soybean [Glycine max (L.) Merr.]; and small grains (Avena spp L., Hordeum vulgare L., Triticum spp L., Secale cereale L., X Triticosecale, and Oryza sativa L.), among others Clonal Repositories Several clonal repositories, some of which are in operation, are being developed for preservation of vegetatively propagated crops such as pears (Pyrus spp L.), stone fruits (Prunus spp L.), hops (Humulus spp L.), mints (Mentha spp L.), citrus (Citrus spp L.), grapes (Vitis spp L.), dates (Phoenix dactylijera L.), apples (Malus spp Mill.), berries (Fragaria spp L., Rubus spp L.), and filberts (Corylus spp L.), etc The Regional Plant Introduction Stations also maintain a limited amount of vegetatively propagated germplasm The National Seed Storage Laboratory A cooperative relationship exists between the Regional Stations, other germplasm curators, and the NSSL Duplicate samples of seed of all plant introductions and other seed propagated germplasm are sent to the 60 BASS NSSL for safe, long-term, backup storage, and maintenance Types of germplasm which are submitted for storage include all introductions, current and obsolete cultivars, inbred lines, some genetic stocks, and any other germplasm stocks considered worthy of long-term preservation in the base collection Because the NSSL is considered to be a long-term or base storage facility, seed from it is not furnished to scientists unless there is no other source Storage conditions in the NSSL are maintained at about -ISOC with the seeds stored in sealed, moisture-barrier packages after having been dried to or % moisture content Seed of each accession is tested for viability before being placed in long-term storage Subsequently, a 5-year germination retest program is followed When seed viability drops to a predetermined level, arrangements are made for production of a new generation with as near as possible the same genetic composition as the original accession In addition to the Regional Plant Introduction Stations, the special curators, the clonal repositories, and the NSSL, which constitutes the NPGS; there are many other collections of plant germplasm in the USA being maintained by commercial plant breeders, colleges and universities, other government agencies, botanic gardens, and other responsible parties The majority of these would be considered to be working collections with those outside the NPGS having no responsibility for either maintaining or distributing germplasm SEED STORAGE BEHAVIOR Most seeds can be classified as either orthodox or recalcitrant according to their response to desiccation Orthodox Seeds Orthodox seeds can be dried to a low moisture content (3 to % ) with little or no loss of viability For most orthodox seeds, the lower the seed moisture content and the lower the storage temperature, within certain limits, the greater the longevity A majority of crop seeds are orthodox Recalcitrant Seeds Recalcitrant seeds cannot ordinarily be dried below certain critical species specific moisture contents without a rapid loss of viability LONG· TERM STORAGE REQUIREMENTS Orthodox Seeds The conditions recommended by IBPGR for storage of base collections are probably most suitable and economical to maintain by conven- GERMPLASM PRESERVATION 61 tional mechanical refrigeration methods (Justice and Bass, 1978; Bass, 1980; Cromarty et al., 1982) The preferred standard for base seed collections is storage at 5% seed moisture content in sealed, moisture-proof containers at -18°C or colder Seed moisture content during storage can be controlled either by predrying to about 5% before sealing in a moisture-proof container or by storage in an adequately dehumidified atmosphere At -18°C an RH of 10 to 15% is required to maintain 5% seed moisture content Because of the cost of dehydration of the storage area, it is more economical to use hermetically sealed containers Also, if the refrigeration or dehumidification equipment should fail, seeds in open storage could gradually increase in moisture content to an unsafe level while seeds in moisture-proof containers would not (Justice and Bass, 1978; Cromarty et aI., 1982) Under certain circumstances a temperature of -lOOC may be acceptable for long-term storage of certain species (Cromarty et aI., 1982) However, such storage could significantly increase the frequency of regeneration and thus result in greater opportunity for loss of genetic diversity and increasing preservation costs For seeds with inherently poor keeping qualities, it may be advisable to use either a seed moisture content lower than % , a temperature colder than -18°C, or both However, seed of some species may be damaged by either too much dehydration or too cold a temperature These points must be verified for each species before very low seed moisture contents and very cold temperatures are used for routine storage of germplasm samples (Bass, 1973, 1979, 1980a, 1980b; 1981) Research in progress at the NSSL has demonstrated that seeds of numerous crops that are air-dried under ambient laboratory temperature and RH conditions (approximately 20°C and 35% RH) can be subjected to freezing at -196°C, the temperature of liquid N (LN2) , and subsequent rewarming with no adverse effects on germination (Stanwood and Bass, 1978, 1981; Stanwood and Roos, 1979; Stanwood, 1980) In a long-term study (50 plus years) involving a large number of genera, species, and cultivars of field crop, vegetable, and flower seeds, tests after years storage showed that, for the kinds of seeds included, storage at -196°C (cryogenic storage) had no adverse effect on germination Typically, an LN2 storage container has a double wall with a vacuum between the walls to provide maximum insulation for the LN2 which is at normal atmospheric pressure Seeds can be stored within the liquid or in the vapor above the liquid Seeds in the liquid will be held at -196°C and seeds in the vapor will be at a temperature of around -150°C There are advantages and disadvantages with regard to both conventional or cryogenic storage Probably the most significant advantages of conventional storage are storage capacity and storage environment, both of which favorably impact sample size, and ease of retrieval The most significant advantages of cryogenic storage are that no electrical equipment is needed and the expected much longer storage life However, just as conventional storage methods require a dependable source of electricity, cryogenic storage requires a dependable source of liquid N The NSSL is doing research on the possible use of liquid N as a storage refrigerant for base collections of germ plasm However, these studies 62 BASS have not been under way long enough to determine the long-term effects of storage in LN2 on either seed longevity or genetic stability In cooperation with Colorado State University, the NSSL has initiated a project to study the cytogenetic effects of cryogenic storage on seeds of barley (Hordeum vulgare L.) and other species Recalcitrant Seeds Recalcitrant seeded species include many important tropical crops (coffee, cocoa, rubber, and anthurium), as well as some temperate crops (wild rice, oak, and walnut) Using presently accepted storage practices, recalcitrant seeds cannot be preserved for long periods of time Consequently, until satisfactory long-term seed storage methods are developed for recalcitrant seeds, the species involved will have to be preserved by cell or tissue culture or in clonal repositories (King and Roberts, 1979; Chin and Roberts, 1980) Preliminary results of research in the NSSL indicate that cryogenic storage may have a place in the long-term preservation of recalcitrant seeds and vegetative propagules once techniques are refined SHORT -TERM STORAGE REQUIREMENTS Orthodox Seeds Storage temperature requirements are usually not as low for working collections as for base collections because of their higher rate of usage and resultant more frequent need for multiplication Also, with working collections people frequently have to spend long periods in the storage room putting up samples for distribution Therefore, employee comfort is of considerable importance Seed samples in working collections are stored in various types of containers such as cloth or paper bags, metal cans, or glass jars Glass jars, although fragile, provide easy visual access to the quantity of seed remaining in a sample Both screw cap glass jars and metal cans provide easy access to the seeds for sample removal A temperature of 5°C and an RH of 35 to 40 % is adequate for most orthodox species for from to 25 years Recalcitrant Seeds Recalcitrant seeds are susceptible to such things as desiccation damage, chilling injury, attack by fungi, and germination during storage Consequently, it is not possible to store most recalcitrant seeds for more than a few days, weeks, or at best, months Even for these short periods of storage, extreme care must be taken in selecting the storage temperature and RH Some species can tolerate a moderately low temperature while others must be kept at a moderately warm temperature Some kinds of seeds formerly throught to be recalcitrant have recently been found to re- GERMPLASM PRESERVATION 63 main viable when dried to a low moisture content Perhaps other apparently recalcitrant seeds can also be dried without damage It is clear that more research is needed on safe storage of recalcitrant seeds DRYING METHODS To attain the required moisture content for hermetic storage, seeds must be either mechanically or chemically dried For best results mechanical drying should be done in a forced, heated air dryer at a temperature no higher than 38°C for a prescribed time dependent upon the kind of seed being dried For chemical drying, either an appropriate amount of a suitable desiccant can be put into an hermetically sealed container, to bring the seeds in the container to the desired moisture content, or a desiccant dehumidifier can be used to adjust the RH to an appropriate level (usually about 10 to 15%) in a drying room maintained at about 15°C with good air circulation (Justice and Bass, 1978; Cromarty et aI., 1982) The possibilities of using freeze drying for preparing germplasm samples for storage has received little attention PACKAGING Glass, metal, or heatsealable aluminum-foil laminates are frequently used as containers for hermetic storage of seeds Glass containers provide excellent moisture protection; however, they are fragile and some types are frequently difficult to seal Metal cans are not fragile and are easy to seal with rather inexpensive sealing equipment However, most cans, except those usually used for paint, have the disadvantage of having to be discarded after opening as they cannot be resealed Heatsealable aluminum-foil laminate containers have the advantages of low cost, recloseability, and more efficient use of storage space Such containers can usually be opened and resealed several times before having to be replaced For storage at a controlled RH, seeds can be packaged in either a paper or cloth container Moisture content of seeds in such containers adjust quite rapidly to changes in RH and/or temperature in the storage room Consequently, seed in cloth or paper containers are less likely to be damaged by rapid changes in storage environment than are seed in moisture resistant packages Packaging in polyethylene or other moisture resistant material is not recommended for either hermetic or controlled atmosphere storage of germplasm samples Thin gauges of polyethylene and other similar materials are moisture resistant, not moisture proof Therefore, seeds packaged in sealed containers of such material and held under high RH conditions can increase in moisture content to a level that would be unsafe if accidentally exposed to too high a temperature Moisture content of seeds sealed in such containers gradually increases or decreases with changes in RH of the storage area Changes in storage temperature can also cause seed moisture content to increase or decrease, but seed moisture content changes may not be rapid enough to prevent damage to seed viability 64 BASS when exposed to relatively high temperatures Thick gauges, 10 to 15 mil of polyethylene and similar materials afford better moisture protection than thin gauges, but even these materials are not moisture proof Use of such materials can give germplasm curators a false sense of security unless they are aware of the shortcomings of most plastic materials (Bass et al., 1961; Justice and Bass, 1978; Cromartyet al., 1982) SAMPLE SIZE There is no universal agreement on what constitutes an adequate sample The IBPGR (1976) recommends that the initial size of each accession in a base collection should, if possible, not be less than 4000 seeds for genetically uniform material and 12 000 seeds for heterogeneous material, and that 1000 and 3000 seeds, respectively, be in duplicate collections in other centers It is also suggested that for very large seeds these quantities may need to be reduced For working collections the sample should be large enough to meet demand without regeneration for a minimum of and, preferably, 10 years When considering what constitutes an adequate sample, factors such as available storage space, cost of constructing additional storage space if and when needed, time in storage, germination retest intervals, number of seeds per germination test, possible distribution frequency, and number of seeds distributed per request have to be taken into account Although a x 100-seed germination test is required for labeling of seed for commercial sale, it is not necessary to use that many seeds for viability monitoring of germplasm samples Because of wide variations that occur in the distribution of weak and dead seeds within samples of many kinds of seeds, it is, however, recommended that a x 100-seed germination test be used whenever possible For small samples of kinds which usually germinate uniformly, a 50-, 25-, or even 20-seed germination test would provide some indication of the viability of the seed lot, but would not provide a measure of variability within the lot Generally, the smaller the number of seed germinated, the greater the possibility of obtaining inaccurate test results Ellis et al (1980) have suggested that gene banks adopt a sequential test procedure for monitoring viability of germplasm accessions Briefly, the sequential germination test procedure suggested is as follows: Germinate a random sample of 40 seeds, if the germination percentage is satisfactory, store or retain in storage; if unsatisfactory, regenerate as soon as possible; if inconclusive, continue the sequential test and use the accumulated germination results to determine when to regenerate A sequential test, although good in theory, could in practice double the work involved in preparing each sample for storage At the NSSL, although it is preferable to start out with a minimum of 10 000 seeds in each accession, the following minimum quantities have been established in cooperation with the appropriate committees of the Crop Science Society of America: 10 000 seeds for small-seeded, 5000 seeds for large-seeded species and cultivars, and 500 seeds for parental GERMPLASM PRESERVATION 65 and germplasm lines and difficult to produce kinds It is understood that the curators of the active collections are responsible for maintaining and distributing germplasm to users, and that the sample in the NSSL will be replaced from time to time by the curator of the active collection to assure that viable seeds are continuously in reserve The quantity of seed stored should permit periodic monitoring of viability and provide seed for regeneration and distribution when necessary The normal germination retest interval used in the NSSL is years; however, a few species known to be long lived are retested on a lO-year schedule As experience is gained, it may be possible to lengthen the time between germination tests for additional species In a gene bank, it is not possible to monitor viability by using a composite sample of a species because of differences in seed longevity among cultivars and accessions Every accession must be individually monitored to guard against loss caused by an especially rapid rate of decline in viability OBJECTIVES OF A BASE COLLECTION The primary objective of a base collection is to preserve indefinitely specific germplasm accessions in order to maintain as broad a germplasm base as possible for the future Another objective of a base collection is to reduce the risk of genetic changes introduced through frequent regeneration Storing too few seeds could increase the frequency of regeneration resulting from depletion of the seed supply, rather than from loss of viability; and, thus increase the possibility of change in the genetic composition of a germ plasm line through accidental means during regeneration, such a cross-pollination, mechanical mixtures, and other similar causes Another objective is to prevent genetic changes in the stored germplasm accessions resulting from excessive deterioration (Roos, 1982) Scientists agree that the frequency of chromosome aberrations in root tips increases with declining viability and vigor, but there is not universal agreement among scientists as to the effect, if any, of these root tip chromosomal aberrations upon the genetic characteristics of plants and seeds produced in subsequent generations Studies conducted at the NSSL (Murata et aI., 1977, 1980, 1981, 1982) indicate that with continued growth of a plant, chromosomal aberrations observed in root tips at first mitosis are eliminated and have no effect upon genetic characteristics of subsequent generations Major concerns of curators of both base and working collections are how many seeds should be planted, how many plants should be pollinated, and how many plants should be harvested for seed for regeneration to assure that all genetic diversity included in the initial seed sample is adequately maintained Factors such as pollination control for inbred lines and cross-pollinated species, disease, insect, and weather related damage, among others, are also of great concern These are of greater concern for heterogeneous accessions than for homogeneous accessions As 66 BASS seed lots deteriorate, there is some natural selection for seed longevity because some genotypes normally lose viability more rapidly than others and some genotypes produce more seeds than others When rapid loss of viability is associated with low seed production, the progeny from a field planting soon shows a marked decrease in the percentage of some genotypes A corresponding marked increase in the percentage of other genotypes will occur unless special precautions are taken to assure that each genotype will be present in the progeny of a regeneration planting in the same ratio as in the original seed sample (Roos, 1977) There is always a possibility of having to plant seed of a given accession more than one time to accomplish successful multiplication; therefore, adequate seeds must be retained for at least two or three multiplication plantings SUMMARY Preservation of crop germplasm is important to future agricultural development To meet the needs of plant breeders and other plant scientists, it is necessary to preserve as broad a germplasm base as possible To prevent as much as possible the occurrence of genetic change during preservation, seed storage conditions must reduce the rate of viability loss to the lowest possible level Regeneration must be accomplished on a timely basis using growing procedures that will assure the continued availability in the same relative proportions of all components of a heterogeneous germplasm accession with a minimum amount of genetic change Cryogenic storage could be a valuable preservation method in the future, especially for small seeds and those that are difficult to produce There is also a possibility that cryogenic storage may be useful in preservation of recalcitrant seeds and other plant propagules, however, much research is needed before routine use of these technologies can become a reality REFERENCES Anonymous 1981 The national plant germplasm system Science and Education, USDA, Washington, DC Bass, L N 1973 Controlled atmosphere and seed storage USDA Seed Quality Research Symposium 1971:463-492 .1979 Physiological aspects of seed preservation p 145 170 In I Rubenstein and R L Phillips (ed.) The plant seed: Development, preservation, and germination Academic Press, New York 1980a Principles of seed storage Modern Government/National Development p 60-64; 67-69; 72-73 1980b Seed viability during long-term storage p 117-141 In Jules Janick (ed.) Horticultural review Vol AVI Publishing Co., Westport, CT 1981 Storage conditions for maintaining seed quality p 239-321 In E E Finney, Jr (ed.) Handbook of transportation and marketing in agriculture, Vol II, Field Crops CRC Press, Boca Raton, FL , Te May Ching, and F L Winter 1961 Packages that protect seeds In USDA Yearbook of Agriculture, "Seeds" :330-338 GERMPLASM PRESERVATION 67 Chin, H F., and E H Roberts 1980 Recalcitrant crop seeds Tropical Press SDN BHD Cromarty, A S., R H Ellis, and E H Roberts 1982 The design of seed storage facilities for genetic conservation IBPGR Secretariat, Rome 10 Ellis, R H., E H Roberts, and J Whitehead 1980.A new, more economic and accurate approach to monitoring the viability of accessions during storage in seed banks Plant genetic resources-News!' 41 IBPGR, Rome, Italy 11 Frankel, O H., and E Bennett 1970 Genetic resources in plants-Their exploration and conservation Handb no 11 Blackwell Scientific Publications, Oxford 12 , and J G Hawkes 1975 Crop genetic resources for today and tomorrow International Biological Programme Cambridge University Press, New York 13 , and Soule 1981 Conservation and evolution Cambridge University Press, New York 14 Hawkes, J G., J T Williams, and Jean Hanson 1976 A bibliography of plant genetic resources IBPGR Secretariat, Rome 15 International Board of Plant Genetics Resources 1975 The conservation of crop genetic resources The Whitefriars Press Ltd., London 16 1976 Report of the working group on engineering, design and cost aspects of longterm seed storage facilities IBPGR, Rome 17 .1982 Annual report IBPGR Secretariat, Rome 18 James, E 1967 Preservation of seed stocks Adv Agron 19:87-106 19 Justice, O L., and L N Bass 1978 Principles and practices of seed storage Agriculture Handb no 506 (Reprinted, Castle House, England 1979) 20 King, M W., and E H Roberts 1979 The storage ofrecalcitrant seeds-achievements and possible approaches IBPGR Secretariat 21 Matsuo, T 1975 Gene conservation-Exploration, collection, preservation and utilization of genetic resources JIBP Synthesis Vo!' Univ of Tokyo Press, Tokyo 22 Murata, M., E E Roos, and T Tsuchiya 1977 Analysis of the first mitotic divisions in germinating seeds of barley Barley Genet News! 7:81-84 23 , , and 1980 Mitotic delay in root tips of peas induced by artificial seed aging Bot Gaz 141(1):19-23 24 , , and 1981 Chromosome damage induced by artificial seed aging in barley Germinability and frequency of aberrant anaphases at first mitosis Can J Genet Cyto! 23:267-280 25 , T Tsuchiya, and E E Roos 1982 Chromosome damage induced by artificial seed aging in barley II Types of chromosomal aberrations at first mitosis Bot Gaz 143(1): 111-116 26 National Academy of Sciences 1972 Genetic vulnerability of major crops National Academy of Sciences, Washington, DC 27 1978 Conservation of germplasm resources-An imperative National Academy of Sciences, Washington, DC 28 Ng, N Q., and J T Williams 1979 Seed stores for genetic conservation IBPGR, Rome 29 Roos, E E 1977 Genetic shifts in bean populations during germplasm preservation Annu Rep Bean Improv Coop 20:47-49 30 1982 Induced genetic changes in seed germplasm during storage p 409-434 In A A Khan (ed.) The physiology and biochemistry of seed development, dormancy, and germination 31 Stanwood, P C 1980 Tolerance of crop seeds to cooling and storage in liquid nitrogen (-196°C) J Seed Techno! 5(1):26 31 32 , and L N Bass 1978 Ultracold preservation of seed germplasm p 361-371 In P Li and A Sakai (ed.) Plant cold hardiness and freezing stress Academic Press, New York 33 , and 1981 Seed germplasm preservation using liquid nitrogen Seed Sci Techno! 9:423-437 34 , and E E Roos 1979 Seed storage of several horticultural species in liquid nitrogen (-196°C) HortScience 14(5) :628-630 [...]... present, stoniness of soil, drainage of site andlor soil Disposition of Materials The final step in organizing the expedition is, as previously stated, the most important and should include a specific plan Arrangements and definitive plans for the receipt and conservation of the collections in national andlor international centers should be made For some crops this system is well organized and very efficient... registry of all plant collections by the office of Plant Introduction (PI) of the USDA After this registration of PI numbers and their entrance into the national catalogue, there is a more or less informal arrangement with members of the research arm of USDA and the state experiment stations for the reproduction and distribution of wild species of Arachis I urge (in accord with the peanut Crops Advisory... structure and sampling methods p 97-107 In O H Frankel and E Bennett (ed.) Genetic resources in plants-Their exploration and conservation IBP Handb no 11 London Blackwell Scientific Publications, Oxford 2 1960 Principles of plant breeding John Wiley & Sons, New York 3 Banks, D J 1976 Peanuts: Germplasm resources Crop Sci 16:499-502 4 Bennett, E 1970 Tactics of plant exploration p 157-180 In O H Frankel and... Africa, and Latin America; some reorganization of support to Southwest Asia, the Mediterranean and South Asia is under way One paradox of work at the regional level is that many minor species assume importance at that level, and the Board with its small budget and staff has to limit its support to such crops Nevertheless, when they are of overriding importance, e.g., the local roots and tubers of the Andes... introductions have reached the hands of American scientists and those of scientists in many other countries More than 200 actual foreign explorations to centers of crop diversity have been undertaken But numbers alone do not tell the story Two years after the Section of Seed and Plant Introduction was created, the rediscovery of Mendel's laws of inheritance triggered the development of plant breeding as a science... acquiring and preserving the genetic diversity of economic plants and their wild relatives The NPGS is pursuing and accelerating programs to acquire, maintain, and evaluate for use as wide as possible a range of genetic diversity of these plants before it is lost forever because of man's adverse impacts on natural environments and changes being made in agricultural patterns and practices Plant germplasm. .. terms of panmictic populations of modern varieties, landraces, and wild relatives) to provide field laboratories for the study of evolution of our crop plants EVALUATION Evaluation of germplasm collections, it is generally agreed, holds highest priority among germplasm functions It would be foolish to say that very little has been done in the way of germplasm evaluation Tens and even hundreds of thousands... T Williams, and N M Anishetty 1983 Crop germplasm conservation and developing countries Science 220: 163-169 10 Van Sloten, D H., and C J Bishop 1982 The IBPGR program for the conservation of horticultural genetic resources 21st Int Hortie Congr., Hamburg September 1982 11 Wilkes, G 1983 Current status of erop plant germplasm CRC Review Plant Sci 1: 133-181 Chapter 3 A National Plant Germplasm System... Revised priorities among crops and regions Rome, Italy 6 1983 Annual report 1982 Rome, Italy 7 , and International Rice Research Institute Rice Advisory Committee 1982 Conservation of the wild rices of tropical Asia Plant Genet Resour Newsl 49: 13-18 8 Ng, Q., and J T Williams 1978 Seed stores for crop genetic conservation Food and Agriculture Organization /International Board for Plant Genetic Resources,... USDA's activities and interests in the introduction of new plants had become so great that a new unit, the Section of Seed and Plant Introduction, was established With a modest beginning and an allotment of $2000, a foundation was laid for an increasing level of activity that has had a profound effect on American agriculture PLANT INTRODUCTIONS (1898-1983) Since 1898, over 400 000 plant introductions ... Copyright © 1984 Crop Science Society of America, 677 South Segoe Road, Madison, WI 53711 Conservation of Crop Germplasm- An International Perspective 35 36 CHANG rising in many African countries... terms of panmictic populations of modern varieties, landraces, and wild relatives) to provide field laboratories for the study of evolution of our crop plants EVALUATION Evaluation of germplasm. .. germplasm (Ng and Williams, 1978) Conservation had to be carried out and the Board began the task of encouraging and assisting countries in the construction of genebanks to handle the major crops